A variety of removable attachments for partial dentures which are supported by adjacent teeth are known in the prior art. More specifically, the attachments commonly used by the dental profession are as follows:
1. The Chayes attachment developed in U.S.A. PA1 2. The Ceka-anchor attachment developed in Belgium. PA1 3. The Inoue attachment development in Japan.
These three attachments have common characteristics in their construction but also have common shortcomings.
They are inconvenient to remove at every mealtime and they are easily damaged due to the mechanical shock inflicted on the abutment teeth they are connected to. They can only be operated with special instruments. Finally, a sudden separation of a loosened partial denture can occur when even small amounts of wear or loosening of the attachment has occurred.
A more detailed explanation of the construction and operation of each of the attachments will illustrate the state of the prior art.
In the Chayes attachment a narrow and deep hole is disposed vertically in the upper side of a crown enclosing an abutment tooth. A protruder is provided at the corner of the partial denture and the protruder engages the vertical hole in the crown. Therefore, the Chayes partial denture is attached to the abutment teeth and prevents movement of the denture both lingually or bucally and left or right. This method of attachment however requires accurate partial denture size and is inconvenient since it is difficult to engage the protruder with a narrow hole each time it is to be attached. Furthermore, it requires the use of special instruments to operate and may only be fabricated from special high cost materials. As a result, both the cost of initial fitting and replacement is undesirably high.
The Ceka type attachment has a female unit joined to the abutment and a vertically oriented male member on the support of the mounted partial denture. It has a disadvantage in that everytime it is removed and reattached there is a great mechanical shock to the abutment tooth. Furthermore, the connector and protruder of this attachment can become worn due to abrasion and their ability to support the denture is thereby weakened. This type of attachment has another disadvantage in that it may not be used if the space available on the abutment tooth is less than 4 millimeters. Finally the cost of using the Ceka type attachment is high because it may only be used with expensive porcelain fused metal crowns.
In the Inoue type attachment a small protruder is mounted on the crown of an abutment tooth and a sleeve and lock pin are formed at the base portion of the partial denture. The lock pin is inserted in the protruder to fix the partial denture. In comparison with the other mentioned methods of attachment this method is comparatively safe but still has significant shortcomings. The sleeve and lock pin are difficult to operate by hand. Great damage can be done to the gingiva during attachment and it may only be used when a unilateral tooth is missing. Finally, this attachment is rather unsightly due to the external exposure of the lock pin.
It is therefore an object of the present invention to provide a removable attachment which does not require fabrication to narrow tolerances or from expensive materials and which may be economically replaced if refitting is necessary.
It is a further object of the present invention to provide an attachment for a partial denture which will not damage the abutting teeth or the gingiva.
Is is another object of the present invention to provide a removable attachment for a partial denture which may be used in a variety of applications including cases where the abutment teeth are few in number or somewhat damaged.
It is yet another object to the present invention to provide a removable attachment for a partial denture which may be installed without the need for specialized instruments, may be easily operated by the user, and is low in cost.
It is a further object of the present invention to provide a removable attachment for a partial denture having a support and a sliding lock member in the form of a tooth and where the sliding lock member has a locking pin which engages a hole in a protruder attached to an abutment tooth to secure the attachment and its denture.
It is an object of the present invention to provide an attachment for a partial denture where the motion of the locking member is limited by a limiting slot and a pin extending from the support member into the limiting slot.
It is a feature of the present invention to provide an attachment which may be used with two sets of artificial molars and being attached by lingual bar or a bar which can be disposed against one or more adjacent crowned natural teeth.
It is a further feature of the present invention to provide an attachment having a lock member which is retained in an opened or closed position by a lock pin resiliently mounted and which engages a detent.